
Server running cost \(E_r+E_w\cdot x\) , where \(E_r\)  is the energy cost of running an idle server for one time slot, and \(E_w\)  is the energy cost per workload unit. Note that \(E_r\)  may account for more than \(50\%\)  of the energy cost in a server [1]}.

Switching cost \(E_s\) , which models the cost of toggling a server between on/off states. As stated in [2]}, if only energy cost matters, then \(E_s\)  is on the order of the cost of running a server for a few seconds to several minutes; if the increased wear-and-tear is accounted for, then \(E_s\)  becomes on the order of the cost of running a server for a hour. In this paper, we use the latter to measure the switching cost \(E_s\) .

